Fix: lock nesting order reversed

The lttng_consumer_stream lock must nest INSIDE the metadata
cache lock, as indicated in the structure's comments
(see consumer.h:340).

CID 1368314 (#1 of 1): Thread deadlock (ORDER_REVERSAL)

Reported-by: Coverity Scan
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/consumer/consumer.c b/src/common/consumer/consumer.c
index 54a0531d5ee80cc87a390d581e796b38c88ced85..234944dad0abf6d6c6594fa68ea64721f1488d87 100644 (file)
--- a/src/common/consumer/consumer.c
+++ b/src/common/consumer/consumer.c
@@ -2051,8 +2051,8 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
        DBG3("Consumer delete metadata stream %d", stream->wait_fd);
 
        pthread_mutex_lock(&consumer_data.lock);
-       pthread_mutex_lock(&stream->chan->lock);
        pthread_mutex_lock(&stream->chan->metadata_cache->lock);
+       pthread_mutex_lock(&stream->chan->lock);
        pthread_mutex_lock(&stream->lock);
 
        /* Remove any reference to that stream. */
@@ -2078,8 +2078,8 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
        stream->chan->metadata_stream = NULL;
 
        pthread_mutex_unlock(&stream->lock);
-       pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
        pthread_mutex_unlock(&stream->chan->lock);
+       pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
        pthread_mutex_unlock(&consumer_data.lock);
 
        if (free_chan) {